Polyisobutylene-based compositions for golf balls

ABSTRACT

Polyisobutylene-based compositions suitable for making golf balls are provided. The amine-terminated polyisobutylene may be reacted with an isocyanate and amine-terminated curing agent to produce a polyurea composition that may be used as a cover material and/or intermediate casing layer. The resulting ball has improved weatherability. In one version, the golf ball includes a polyurea casing layer and polyurea cover. In a second version, the golf ball includes an ionomer casing layer and polyurea cover. In yet another version, the golf ball includes a polyurea casing layer and ionomer cover.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to polyisobutylene-based compositions that may be used to make golf balls. More particularly, a polyurea composition may be prepared by the reaction of an isocyanate, amine-terminated polyisobutylene, and amine-terminated curing agent. The resulting compositions have many advantageous properties and can be used as a cover material and/or intermediate casing layer in the construction of a golf ball.

2. Brief Review of the Related Art

The golf industry continues to look at polyurethane and polyurea compositions as materials for making golf balls. There is strong interest in polyurethanes and polyureas, because they can be used as golf ball cover materials and may provide the ball with an optimum combination of “hard” and “soft” properties. Improved durability, toughness, and abrasion-resistance are some of the desired hard properties. The soft properties provide the player with a better “feel” when he/she strikes the ball with the club face. With golf balls having a good feel, the player senses more control as the club face makes impact with the ball. The hard properties of the ball help players achieve greater flight distance with their shots. While the softer feel of the ball allows players to place a spin on the ball and better control its flight pattern.

Cover materials for golf balls may be made of various polyurethane compositions. Basically, polyurethane compositions contain urethane linkages that are formed by reacting an isocyanate group (—N═C═O) with a hydroxyl group (OH). Commercial polyurethanes are produced by the reaction of an isocyanate having two or more functional groups with a polyalcohol(polyol) in the presence of a catalyst and other additives. The chain length of the polyurethane is extended by reacting the prepolymer with a curing agent. The resulting polymer has elastomeric properties, because of its “hard” and “soft” segments, which are covalently bonded together. The soft, amorphous, low-melting point segments, which are formed from the polyols, are relatively flexible and mobile, while the hard, high-melting point segments, which are formed from the isocyanate and chain extenders, are relatively stiff and immobile. The phase separation of the hard and soft segments provides the polymer with its elastomeric resiliency.

Polyurea compositions, which are distinct from the above-described polyurethanes, also are used in cover materials. Polyurea compositions contain urea linkages that are formed by reacting an isocyanate group (—N═C═O) with an amine group (NH or NH₂). The chain length of the polyurea is extended by reacting the prepolymer with an amine-terminated curing agent. The resulting polyurea also has elastomeric properties because of its “hard” and “soft” segments.

Polyurethane and polyurea compositions, suitable for use in making components of golf balls, are described in the patent literature. For example, Wu, U.S. Pat. No. 5,484,870 discloses a polyurea composition suitable for molding golf ball covers. The polyurea composition is the reaction product of an organic compound having at least two isocyanate functional groups and an amine curing agent. The mole equivalent ratio of amine groups to isocyanate groups may vary over a wide range. Additional materials such as colorants, ultraviolet light absorbers, plasticizers, and the like may be included in the compositions.

Bulpett et al., U.S. Pat. No. 6,964,621 discloses polyurea compositions that can be used in the construction of golf balls. The compositions are prepared from a polyurea prepolymer and amine curing agent. According to the '621 Patent, the resulting golf ball has improved cut and shear resistance.

Although conventional polyurethane and polyurea compositions are generally suitable for use in making golf balls, one potential problem is the compositions may suffer from hydrolytic and oxidative breakdown in some instances. For example, if a polyether polyol or polyester polyol is used to form the polyurethane polymer, the product may contain hydrophilic segments having relatively poor hydrolytic stability. The resulting golf ball cover material may have poor water-resistance. In addition, the polyether and polyester-based polyurethanes may be more susceptible to oxidative breakdown. Thus, it would be desirable to develop a composition having more hydrolytic and oxidative stability along with improved hydrophobicity that could be used in golf ball constructions, particularly covers. The present invention provides such compositions and golf balls made from such compositions.

SUMMARY OF THE INVENTION

The present invention provides a golf ball having a core, a polyurea intermediate casing layer, and a polyurea cover material. The polyurea intermediate layer is made of a composition, which is the reaction product of ingredients comprising a first isocyanate, first amine-terminated polyisobutylene, and first amine-terminated cross-linking agent. The polyurea cover material is made of a composition, which is the reaction product of ingredients comprising a second isocyanate, second amine-terminated polyisobutylene, and second amine-terminated cross-linking agent. The resulting polyurea compositions have high mechanical strength and integrity. In addition, the polymers have good weatherability with improved resistance to the effects of water and heat exposure as well as enhanced ultraviolet (UV) light-stability. In another version, the golf ball includes a polybutadiene core, an intermediate layer made of an ionomer resin, and a cover layer made of the polyurea composition.

Golf balls having various constructions may be made in accordance with this invention. In one embodiment, the golf ball core has a diameter of about 1.20 to about 1.60 inches; the intermediate layer has a thickness of about 0.035 to about 0.060 inches; and the cover has a thickness of about 0.020 to about 0.040 inches. The different components comprising the golf ball may be of different hardness depending upon the desired properties of the ball. For example, in one version, the golf ball core has a surface hardness of about 30 to about 65 Shore D, while the intermediate layer has a material hardness of about 45 to about 80 Shore D and the cover layer has a material hardness of about 40 to about 65 Shore D.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention are set forth in the appended claims. However, the preferred embodiments of the invention, together with further objects and attendant advantages, are best understood by reference to the following detailed description in connection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a single-layered, two-piece golf ball made in accordance with the present invention;

FIG. 2 is a cross-sectional view of a multi-layered, three-piece golf ball containing a polyurea intermediate layer and polyurea cover made in accordance with the present invention;

FIG. 3 is a cross-sectional view of a multi-layered, four-piece golf ball containing a two-piece core, polyurea intermediate layer, and polyurea cover made in accordance with the present invention;

FIG. 4 is a cross-sectional view of a multi-layered, three-piece golf ball containing a polyurea cover and non-polyurea intermediate layer made in accordance with the present invention; and

FIG. 5 is a cross-sectional view of a multi-layered, three-piece golf ball containing a polyurea intermediate layer and non-polyurea cover made in accordance with the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to golf balls having a cover material and/or intermediate layer made from a polyurea composition. In general, polyurea compositions contain urea linkages formed by reacting an isocyanate group with an amine group. The chain length of the polyurea prepolymer is extended by reacting the prepolymer with an amine-terminated curing agent. The resulting polyurea polymer has elastomeric properties, because of its “hard” and “soft” segments, which are covalently bonded together. The soft, amorphous, low-melting point segments, formed from the polyamines, are relatively flexible and mobile, while the hard, high-melting point segments, formed from the isocyanate and chain extenders, are relatively stiff and immobile. The phase separation of the hard and soft segments provides the polymer with its elastomeric resiliency. When the polyurea prepolymer is cured using amine-terminated compounds, the resulting polymer contains only urea linkages.

However, if a hydroxyl-terminated curing agent is used, any excess isocyanate groups in the prepolymer will react with the hydroxyl groups in the curing agent and create urethane linkages. That is, a polyurea/polyurethane hybrid composition is produced, which is distinct from a pure polyurea composition. It also should be understood that pure polyurethane is a significantly different material. Polyurethanes contain urethane linkages formed by reacting an isocyanate group with a hydroxyl group. Commercial polyurethane materials are produced by the reaction of an isocyanate with a polyalcohol(polyol) in the presence of a catalyst and other additives to form a prepolymer. The chain length of the polyurethane prepolymer is extended by reacting it with a hydroxyl or amine-terminated curing agent.

Any suitable isocyanate known in the art can be used to produce the polyurea compositions in accordance with this invention. Such isocyanates include, for example, aliphatic, cycloaliphatic, aromatic aliphatic, aromatic, any derivatives thereof, and combinations of these compounds having two or more isocyanate (—N═C═O) groups per molecule. The isocyanates may be organic polyisocyanate-terminated prepolymers, low free isocyanate prepolymers, and mixtures thereof. The isocyanate-containing reactable component also may include any isocyanate-functional monomer, dimer, trimer, or polymeric adduct thereof, prepolymer, quasi-prepolymer, or mixtures thereof. Isocyanate-functional compounds may include monoisocyanates or polyisocyanates that include any isocyanate functionality of two or more.

Preferred isocyanates include diisocyanates (having two NCO groups per molecule), biurets thereof, dimerized uretdiones thereof, trimerized isocyanurates thereof, and polyfunctional isocyanates such as monomeric triisocyanates. Diisocyanates typically have the generic structure of OCN—R—NCO. Exemplary diisocyanates include, but are not limited to, unsaturated isocyanates such as: p-phenylene diisocyanate (“PPDI,” i.e., 1,4-phenylene diisocyanate), m-phenylene diisocyanate (“MPDI,” i.e., 1,3-phenylene diisocyanate), o-phenylene diisocyanate (i.e., 1,2-phenylene diisocyanate), 4-chloro-1,3-phenylene diisocyanate, toluene diisocyanate (“TDI”), m-tetramethylxylene diisocyanate (“m-TMXDI”), p-tetramethylxylene diisocyanate (“p-TMXDI”), 1,2-, 1,3-, and 1,4-xylene diisocyanates, 2,2′-, 2,4′-, and 4,4′-biphenylene diisocyanates, 3,3′-dimethyl-4,4′-biphenylene diisocyanate (“TODI”), 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanates (“MDI”), 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, carbodiimide-modified MDI, polyphenylene polymethylene polyisocyanate (“PMDI,” i.e., polymeric MDI), 1,5-naphthalene diisocyanate (“NDI”), 1,5-tetrahydronaphththalene diisocyanate, anthracene diisocyanate, tetracene diisocyanate; and saturated isocyanates such as: 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate (“HDI”) and isomers thereof, 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanates, 1,7-heptamethylene diisocyanate and isomers thereof, 1,8-octamethylene diisocyanate and isomers thereof, 1,9-novamethylene diisocyanate and isomers thereof, 1,10-decamethylene diisocyanate and isomers thereof, 1,12-dodecane diisocyanate and isomer thereof, 1,3-cyclobutane diisocyanate, 1,2-, 1,3-, and 1,4-cyclohexane diisocyanates, 2,4- and 2,6-methylcyclohexane diisocyanates (“HTDI”), isophorone diisocyanate (“IPDI”), isocyanatomethylcyclohexane isocyanate, isocyanatoethylcyclohexane isocyanate, 4,4′-dicyclohexylmethane diisocyanate (“H₁₂ MDI,” i.e., bis(4-isocyanatocyclohexyl)-methane), and 2,4′- and 4,4′-dicyclohexane diisocyanates. Dimerized uretdiones of diisocyanates and polyisocyanates include, for example, unsaturated isocyanates such as uretdiones of toluene diisocyanates, uretdiones of diphenylmethane diisocyanates; and saturated isocyanates such as uretdiones of hexamethylene diisocyanates. Trimerized isocyanurates of diisocyanates and polyisocyanates include, for example, unsaturated isocyanates such as trimers of diphenylmethane diisocyanate, trimers of tetramethylxylene diisocyanate, isocyanurates of toluene diisocyanates; and saturated isocyanates such as isocyanurates of isophorone diisocyanate, isocyanurates of hexamethylene diisocyanate, isocyanurates of trimethyl-hexamethylene diisocyanates. Monomeric triisocyanates include, for example, unsaturated isocyanates such as 2,4,4′-diphenylene triisocyanate, 2,4,4′-diphenylmethane triisocyanate, 4,4′,4″-triphenylmethane triisocyanate; and saturated isocyanates such as: 1,3,5-cyclohexane triisocyanate. Preferably, the isocyanate is selected from the group consisting of MDI, H₁₂MDI, PPDI, TDI, IPDI, HDI, NDI, XDI, TMXDI, THDI, and TMDI, and homopolymers and copolymers and mixtures thereof.

As discussed above, polyurea is an elastomeric material that is the reaction product of an isocyanate component and amine-terminated polymer resin. As described further below, of the many possible amine-terminated compounds that can be used in the reaction process, it was found that amine-terminated polyisobutylene can be reacted with the isocyanate to provide a polyurea composition having the most desirable properties for purposes of this invention. In general, the amine-terminated polyisobutylene compound has the following generic structural formula:

It has been found that the amine-terminated polyisobutylenes of this invention can be reacted with isocyanates to produce polyureas having high mechanical strength and integrity. Moreover, the amine-terminated polyisobutylenes have enhanced hydrolytic stability, and it is believed this contributes to the resulting polyurea composition having enhanced moisture-resistance. The polyisobutylene-based polyureas do not have any ether or ester linkages along the carbon chain. The carbon-carbon bonds making up the polyisobutylene chain are less susceptible to hydrolysis and degradation. That is, there are less moisture attack sites along the carbon chain. It is less likely that moisture will attack the polyisobutylene chain and break-up the chain into smaller, weaker chains. Thus, the resulting polymers have good weather resistance. The polymers show high resistance to the effects of water and heat exposure as well as enhanced ultraviolet (UV) light-stability.

There are two basic techniques that can be used to make the polyurea elastomers of this invention: a) one-shot technique, and b) prepolymer technique. In the one-shot technique, the isocyanate, amine-terminated compound, and amine-terminated curing agent are reacted in one step. Meanwhile, the prepolymer technique involves a first reaction between the isocyanate and amine-terminated compound to produce a polyurea prepolymer, and a subsequent reaction between the prepolymer and amine-terminated curing agent. As a result of the reaction between the isocyanate and amine-terminated polyisobutylene, there will be some unreacted NCO groups in the polyurea prepolymer. As the weight percent of unreacted isocyanate groups increases, the hardness of the composition also generally increases. Either the one-shot or prepolymer method may be employed to produce the polyurea compositions of the invention; however, the prepolymer technique is preferred because it provides better control of the chemical reaction. The prepolymer method provides a more homogeneous mixture resulting in a more consistent polymer composition. The one-shot method results in a mixture that is inhomogeneous (more random) and affords the manufacturer less control over the molecular structure of the resultant composition.

In the casting process, the polyurea composition may be formed by chain-extending the polyurea prepolymer with a single curing agent or a blend of curing agents as described further below. The compositions of the present invention may be selected from among both castable thermoplastic and thermoset materials. Thermoplastic polyurea compositions are typically formed by reacting the isocyanate and amine-terminated compound, each having two (or less) functional groups, at a 1:1 stoichiometric ratio. For example, a prepolymer may be cured with a secondary diamine to make the non-cross-linked thermoplastic composition. Thermoset compositions, on the other hand, are cross-linked polymers and are typically produced from the reaction of an isocyanate and amine-terminated compound, wherein each component has two (or greater) functional groups, at normally a 1.05:1 stoichiometric ratio. For example, a prepolymer may be cured with a primary or secondary diamine to make the cross-linked thermoset polyureas. In general, thermoset polyurea compositions are easier to prepare than thermoplastic polyureas.

In a preferred embodiment, a pure polyurea composition is prepared. That is, the composition contains only urea linkages. An amine-terminated curing agent is used in the reaction to produce the pure polyurea composition. However, it should be understood that a polyurea/urethane hybrid composition may be prepared in accordance with this invention in some instances. Such a hybrid composition could be obtained if the polyurea prepolymer were cured with a hydroxyl-terminated curing agent. Any excess isocyanate in the polyurea prepolymer reacts with the hydroxyl groups in the curing agent and forms urethane linkages. The resulting polyurea/urethane hybrid composition contains both urea and urethane linkages.

Suitable amine-terminated curing agents that can be used for chain-extending the polyurea prepolymer of this invention include, but are not limited to, unsaturated diamines such as 4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-dianiline or “MDA”), m-phenylenediamine, p-phenylenediamine, 1,2- or 1,4-bis(sec-butylamino)benzene, 3,5-diethyl-(2,4- or 2,6-)toluenediamine or “DETDA”, 3,5-dimethylthio-(2,4- or 2,6-)toluenediamine, 3,5-diethylthio-(2,4- or 2,6-)toluenediamine, 3,3′-dimethyl-4,4′-diamino-diphenylmethane, 3,3′-diethyl-5,5′-dimethyl4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine)), 3,3′-dichloro-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2-chloroaniline) or “MOCA”), 3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaniline), 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”), 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane, or “MDEA”), 3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diamino-diphenylmethane, 3,3′-dichloro-4,4′-diamino-diphenylmethane, 4,4′-methylene-bis(2,3-dichloroaniline) (i.e., 2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane or “MDCA”), 4,4′-bis(sec-butylamino)-diphenylmethane, N,N′-dialkylamino-diphenylmethane, trimethyleneglycol-di(p-aminobenzoate), polyethyleneglycol-di(p-aminobenzoate), polytetramethyleneglycol-di(p-aminobenzoate); saturated diamines such as ethylene diamine, 1,3-propylene diamine, 2-methyl-pentamethylene diamine, hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine, imino-bis(propylamine), imido-bis(propylamine), methylimino-bis(propylamine) (i.e., N-(3-aminopropyl)-N-methyl-1,3-propanediamine), 1,4-bis(3-aminopropoxy)butane (i.e., 3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine), diethyleneglycol-bis(propylamine) (i.e., diethyleneglycol-di(aminopropyl)ether), 4,7,10-trioxatridecane-1,13-diamine, 1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane, poly(oxyethylene-oxypropylene)diamines, 1,3- or 1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or 1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophorone diamine, 4,4′-diamino-dicyclohexylmethane, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, N,N′-dialkylamino-dicyclohexylmethane, polyoxyethylene diamines, 3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane, polyoxypropylene diamines, 3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane, polytetramethylene ether diamines, 3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane (i.e., 4,4′-methylene-bis(2,6-diethylaminocyclohexane)), 3,3′-dichloro-4,4′-diamino-dicyclohexylmethane, 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane, (ethylene oxide)-capped polyoxypropylene ether diamines, 2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane, 4,4′-bis(sec-butylamino)-dicyclohexylmethane; triamines such as diethylene triamine, dipropylene triamine, (propylene oxide)-based triamines (i.e., polyoxypropylene triamines), N-(2-aminoethyl)-1,3-propylenediamine (i.e., N₃-amine), glycerin-based triamines, (all saturated); tetramines such as N,N′-bis(3-aminopropyl)ethylene diamine (i.e., N₄-amine) (both saturated), triethylene tetramine; and other polyamines such as tetraethylene pentamine (also saturated). It also is recognized that the amine-terminated polyisobutylene materials of this invention can be used as the amine curing agent in some instances.

As discussed above, in some instances, it may be desirable to form a polyurea/polyurethane hybrid composition. In such circumstances, the curing agent used in the reaction of the polyurea prepolymer may be selected from the group consisting of hydroxyl-terminated curing agents and mixtures of amine-terminated and hydroxyl-terminated curing agents.

The hydroxyl-terminated curing agents are preferably selected from the group consisting of ethylene glycol; diethylene glycol; polyethylene glycol; propylene glycol; 2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol; monoethanolamine; diethanolamine; triethanolamine; monoisopropanolamine; diisopropanolamine; dipropylene glycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol; trimethylolpropane; cyclohexyldimethylol; triisopropanolamine; N,N,N′,N′-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycol bis-(aminopropyl)ether; 1,5-pentanediol; 1,6-hexanediol; 1,3-bis-(2-hydroxyethoxy)cyclohexane; 1,4-cyclohexyldimethylol; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]cyclohexane; 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane; trimethylolpropane; polytetramethylene ether glycol, preferably having a molecular weight from about 250 to about 3900; and mixtures thereof.

Additional materials, as known in the art, may be added to the polyurea compositions. These additional materials include, but are not limited to, catalysts, wetting agents, coloring agents, optical brighteners, cross-linking agents, whitening agents such as titanium dioxide and zinc oxide, ultraviolet (UV) light absorbers, hindered amine light stabilizers, defoaming agents, processing aids, surfactants, and other conventional additives. For example, wetting additives may be added to more effectively disperse the pigments. Antioxidants, stabilizers, softening agents, plasticizers, including internal and external plasticizers, impact modifiers, foaming agents, density-adjusting fillers, reinforcing materials, and compatibilizers also may be added to the composition in amounts known in the art. Generally, the additives will be present in the composition in an amount between about 1 and about 70 weight percent based on the total weight of the composition depending upon the desired properties.

A catalyst also may be employed to promote the reaction between the prepolymer and the curing agent to make the polyurea composition. Suitable catalysts include, but are not limited to bismuth catalyst; zinc octoate; stannous octoate; tin catalysts such as bis-butyltin dilaurate, bis-butyltin diacetate, stannous octoate; tin (II) chloride, tin (IV) chloride, bis-butyltin dimethoxide, dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctyl mercaptoacetate; amine catalysts such as triethylenediamine, triethylamine, and tributylamine; organic acids such as oleic acid and acetic acid; delayed catalysts; and mixtures thereof. The catalyst is preferably added in an amount sufficient to catalyze the reaction of the components in the reactive mixture. In one embodiment, the catalyst is present in an amount from about 0.001 percent to about 5 percent by weight of the composition.

Preferably, the polymer matrix is a pure polyurea composition. That is, the polymer composition contains only urea linkages having the following general structure:

However, as discussed above, it is recognized that a polyurea/urethane hybrid composition also may be prepared in accordance with this invention. This occurs if the polyurea prepolymer is cured with hydroxyl-terminated curing agents. Any excess isocyanate in the polyurea prepolymer reacts with the hydroxyl groups in the curing agent and forms urethane linkages. The resulting polyurea/polyurethane composition contains both urea linkages (as described above) and urethane linkages, wherein the urethane linkages have the following general structure:

The polyurea materials of this invention may be used with any type of ball construction known in the art. Such golf ball designs include, for example, two-piece, three-piece, and four-piece designs. The core, intermediate casing, and cover portions making up the golf ball each can be single or multi-layered. Referring to FIG. 1, a single layered (two-piece) golf ball (5) having a solid core (12) and polyurea cover (14) of this invention is shown. FIG. 2 shows a multi-layered (three-piece) golf ball (15) that can be made in accordance with this invention. In this version, the ball (15) includes a solid core (18), an intermediate casing layer (20), and cover layer (22), wherein the intermediate casing layer (20) and cover layer (22) are each made of the polyurea composition of this invention.

Core Segment

The core segments (12, 18) in the golf balls (5, 15) shown in FIGS. 1 and 2, respectively, are typically made from compositions containing a base rubber, filler, initiator agent, and cross-linking agent. The base rubber normally is a natural or synthetic rubber, such as polybutadiene rubber. In one embodiment, the base rubber is 1,4-polybutadiene having a cis-structure of at least 40%. The polybutadiene can be blended with other elastomers such as natural rubber, polyisoprene rubber, styrene-butadiene rubber and/or other polybutadienes. Another suitable rubber that may be used in the core is trans-polybutadiene. This polybutadiene isomer is formed by converting the cis-isomer of the polybutadiene to the trans-isomer during a molding cycle. A soft and fast agent such as pentachlorothiophenol (PCTP) or ZnPCTP can be blended with the polybutadiene. These compounds may also function as cis-to-trans catalysts to convert some cis-1,4 bonds in the polybutadiene into trans 1,4 bonds. Fillers, which may be used to modify such properties as the specific gravity, density, hardness, weight, modulus, resiliency, compression, and the like may be added to the core composition. Normally, the fillers are inorganic, and suitable fillers include numerous metals or metal oxides, such as zinc oxide and tin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate, barium carbonate, clay, tungsten, tungsten carbide, silica, and mixtures thereof.

In FIGS. 1 and 2, the core portions (12, 18) are shown as single-piece structures made from a natural or synthetic rubber composition such as polybutadiene. In other instances, a multi-piece core may be constructed; that is, there may be two or more core portions or segments. For example, in FIG. 3, a golf ball (25) having a two-piece solid core (24, 26), intermediate layer (28), and a cover layer (30) made in accordance with this invention is shown. The multi-layered core (constituting inner and outer core segments {24, 26}) may be referred to as the “center” of the ball. The inner core portion (24) may be made of a first base rubber material and the outer core layer (26), which surrounds the inner core (24), may be made of a second base rubber material. The respective core pieces (24, 26) may be made of the same or different rubber materials as described above. Cross-linking agents and fillers may be added to the rubber materials of each core piece.

Intermediate Layer

As shown in FIGS. 2 and 3, the golf balls (15, 25) may include intermediate layers (20, 28), respectively, made of the polyurea composition of this invention. As used herein, the term, “intermediate layer” means a layer of the ball disposed between the core and cover. The intermediate layer may be considered an outer core layer or inner cover layer or any other layer disposed between the inner core and outer cover of the ball. The intermediate layer also may be referred to as a casing or mantle layer. Furthermore, it should be understood that the ball may include one or more intermediate layers. In FIGS. 2 and 3, the intermediate layers (20, 28) are shown encapsulating and enveloping the respective cores (18, 26). The overlying intermediate layers (20, 28) are positioned between the respective cores (18, 26) and cover layers (22, 30). It is anticipated that when the polyurea composition of this invention is used to form the intermediate layers (20, 28), the resulting layer will have good moisture-resistance. The polyurea layer should prevent liquid and/or vapor from penetrating into the core segments.

Referring now to FIG. 4, one alternative version of a golf ball made in accordance with this invention is shown. Here, the intermediate layer (36) is shown made of a conventional thermoplastic or thermosetting composition as opposed to the polyurea material of this invention. In the embodiment represent in FIG. 4, the cover layer (38), but not the intermediate layer (36), is made of the polyurea material of this invention.

If one desires to construct the golf ball so it contains an intermediate layer (36) made of an ordinary resin material and a cover layer (38) made of the polyurea composition of this invention, as shown in FIG. 4, then the resin used for the intermediate layer may be selected from a variety of thermoplastic and thermosetting materials. Suitable thermoplastic compositions include, but are not limited to, partially- and fully-neutralized ionomers, graft copolymers of ionomer and polyamide, and the following non-ionomeric polymers: polyesters; polyamides; polyamide-ethers, and polyamide-esters; polyurethanes, polyureas, and polyurethane-polyurea hybrids; fluoropolymers; non-ionomeric acid polymers, such as E/Y— and E/X/Y-type copolymers, wherein E is an olefin (e.g., ethylene), Y is a carboxylic acid, and X is a softening comonomer such as vinyl esters of aliphatic carboxylic acids, and alkyl alkylacrylates; metallocene-catalyzed polymers; polystyrenes; polypropylenes and polyethylenes; polyvinyl chlorides and grafted polyvinyl chlorides; polyvinyl acetates; polycarbonates including polycarbonate/acrylonitrile-butadiene-styrene blends, polycarbonate/polyurethane blends, and polycarbonate/polyester blends; polyvinyl alcohols; polyethers; polyimides, polyetherketones, polyamideimides; and mixtures of any two or more of the above thermoplastic polymers.

Examples of commercially available thermoplastics include, but are not limited to: Pebax® thermoplastic polyether block amides, commercially available from Arkema Inc.; Surlyn® ionomer resins, Hytrel® thermoplastic polyester elastomers, and ionomeric materials sold under the trade names DuPont® HPF 1000 and HPF 2000, all of which are commercially available from E. I. du Pont de Nemours and Company; Iotek® ionomers, commercially available from ExxonMobil Chemical Company; Amplify® IO ionomers of ethylene acrylic acid copolymers, commercially available from The Dow Chemical Company; Clarix® ionomer resins, commercially available from A. Schulman Inc.; Elastollan® polyurethane-based thermoplastic elastomers, commercially available from BASF; and Xylex® polycarbonate/polyester blends, commercially available from SABIC Innovative Plastics. The additives and filler materials described above may be added to the intermediate layer composition to modify such properties as the specific gravity, density, hardness, weight, modulus, resiliency, compression, and the like.

The ionomeric resins may be blended with non-ionic thermoplastic resins. Examples of suitable non-ionic thermoplastic resins include, but are not limited to, polyurethane, poly-ether-ester, poly-amide-ether, polyether-urea, thermoplastic polyether block amides (e.g., Pebax® block copolymers, commercially available from Arkema Inc.), styrene-butadiene-styrene block copolymers, styrene(ethylene-butylene)-styrene block copolymers, polyamides, polyesters, polyolefins (e.g., polyethylene, polypropylene, ethylene-propylene copolymers, polyethylene-(meth)acrylate, polyethylene-(meth)acrylic acid, functionalized polymers with maleic anhydride grafting, Fusabond® functionalized polymers commercially available from E. I. du Pont de Nemours and Company, functionalized polymers with epoxidation, elastomers (e.g., ethylene propylene diene monomer rubber, metallocene-catalyzed polyolefin) and ground powders of thermoset elastomers.

In one version of the golf ball, as shown in FIGS. 2-3 and 5, and which is described further below, the polymer matrix constituting the respective intermediate layers (20, 28, and 42) consists of 100% by weight of the polyurea composition of this invention. However, as discussed above, it is recognized that a polyurea/urethane hybrid composition also may be prepared in accordance with this invention. Thus, in another version of the golf ball, the polymer matrix of the respective intermediate layers (20, 28, and 42) may be a polyurea/polyurethane hybrid blend. In one example, the blend contains about 10 to about 90% by weight of the polyurea composition and about 90% to about 10% of a polyurethane composition. In yet another embodiment, the polymer matrix making up the respective intermediate layers (20, 28, and 42) is a blend of about 10 to about 90% by weight of the polyurea composition and about 90% to about 10% of another polymer such as, for example, vinyl resins, polyesters, polyamides, or polyolefins.

Cover Layer

As shown in FIGS. 1-4, the respective cover layers (14, 22, 30, and 38) may be made of the polyurea composition of this invention. In FIG. 1, the polyurea cover layer (14) is shown immediately encapsulating and enveloping the core (12). In FIGS. 2-4, the respective polyurea cover layers (22, 30, and 38) are shown immediately surrounding the underlying intermediate layers (20, 28, and 36). It is anticipated that cover materials made with the polyurea compositions of this invention will have several advantageous properties and benefits including the following. First, the cover materials will show good moisture-resistance. While not wishing to be bound by any theory, it is believed the hydrophobic backbone of the amine-terminated polyisobutylene used to produce the polyurea composition, as described above, may significantly contribute to this enhanced moisture resistance. Secondly, it is expected that the polyurea cover materials will have high durability and impact-resistance.

Referring now to FIG. 5, one alternative version of a golf ball (45) made in accordance with this invention is shown. Here, the cover layer (44) is shown made of a conventional thermoplastic or thermosetting composition, and the intermediate layer (42) is made of the polyurea composition of this invention.

The thermoplastic or thermosetting compositions described above, as opposed to the polyurea, may be used to form the cover layer (44) shown in FIG. 5. In addition, the above filler materials may be added to the cover layer composition to modify such properties as, for example, the specific gravity, density, hardness, weight, modulus, resiliency, compression, and the like.

In one version of the golf ball, as shown in FIGS. 1-4, the polymer matrix constituting the respective cover layers (14, 22, 30, and 38) consists of 100% by weight of the polyurea composition of this invention. However, as discussed above, it is recognized that a polyurea/urethane hybrid composition also may be prepared in accordance with this invention. Thus, in another version, the polymer matrix of the respective cover layers (14, 22, 30, and 38) is a polyurea/polyurethane hybrid blend. The blend contains about 10 to about 90% by weight of the polyurea composition and about 90% to about 10% of a polyurethane composition. In yet another embodiment, the polymer matrix making up the respective cover layers (14, 22, 30, and 38) is a blend of about 10 to about 90% by weight of the polyurea composition and about 90% to about 10% of another polymer or material such as, for example, vinyl resins, polyesters, polyamides, or polyolefins.

Construction

Golf balls made in accordance with this invention can be of any size, although the USGA requires that golf ball used in competition have a diameter of at least 1.68 inches and a weight of no greater than 1.62 ounces. For play outside of USGA competition, the golf balls can have smaller diameters and be heavier. Preferably, the diameter of the golf ball is in the range of about 1.68 to about 1.80 inches. The core generally will have a diameter in the range of about 1.26 to about 1.60 inches. In one preferred version, the single-piece core has a diameter of about 1.57 inches. The hardness of the core may vary depending upon the desired properties of the ball. In general, core hardness is in the range of about 30 to about 65 Shore D and more preferably in the range of about 35 to about 60 Shore D. The compression of the core portion is generally in the range of about 70 to about 1 10 and more preferably in the range of about 80 to about 100. As shown in FIGS. 1-5, the core portions generally makes up a substantial portion of the ball, for example, the core may constitute at least 95% or greater of the ball structure.

Referring to FIGS. 2-5, which show golf balls having intermediate casing layers, the range of thicknesses for the casing layer can vary because different materials can be used. In general, however, the thickness of the casing layer will be in the range of about 0.015 to about 0.120 inches. More particularly, if the above-described polyurea composition is used to make the casing layer, the thickness of the casing layer will be in the range of about 0.035 to about 0.060 inches. Preferably, the overall diameter of the core and all intermediate layers is about 90 percent to about 98 percent of the overall diameter of the finished ball.

As shown in FIGS. 1-5 and described above, the cover layer is preferably made of the polyurea composition of this invention, although other materials may be used in some instances. The cover layer should help provide the ball with good mechanical strength and durability as well as playing performance properties. The thickness of the cover layer may vary, but it is generally in the range of about 0.015 to about 0.090 inches. More particularly, if the above-described polyurea composition is used to make the cover layer, the thickness of the cover layer will be in the range of about 0.020 to about 0.040 inches.

The golf balls of this invention may contain layers having the same hardness or different hardness values. Surface hardness and material hardness are important properties considered in ball design and construction. In general, the hardness of the surface or material refers to its firmness. The test methods for measuring surface hardness and material hardness are described in further detail below. There can be uniform hardness throughout the different layers of the ball or there can be hardness gradients across the layers. For example, the hardness of the core may vary, but it is generally in the range of about 30 to about 65 Shore D and more preferably in the range of about 35 to about 60 Shore D. The intermediate layer(s) may also vary in hardness in accordance with the present invention. In one embodiment, when the polyurea material of this invention is used to form the intermediate layer, the material hardness is about 45 to about 80 Shore D. Similarly, the hardness of the cover may vary, but it is generally in the range of about 30 to about 65 Shore D. For example, in one version, when the polyurea material of this invention is used to form the cover, the material hardness is about 40 to about 65 Shore D.

The golf balls of this invention may be constructed using any suitable technique known in the art. These methods generally include compression molding, flip molding, injection molding, retractable pin injection molding, reaction injection molding (RIM), liquid injection molding (LIM), casting, vacuum forming, powder coating, flow coating, spin coating, dipping, spraying, and the like.

More particularly, the core of the golf ball may be formed using compression molding or injection molding. As discussed above, suitable core materials include thermoset materials, such as, for example, rubber, styrene butadiene, polybutadiene, isoprene, polyisoprene, trans-isoprene, as well as thermoplastics such as, for example, ionomer resins, polyamides or polyesters. The intermediate casing layer, which may be made of the polyurea composition of this invention or other polymers such as ionomer resins, may be formed using known methods such as retractable pin injection molding or compression molding.

The intermediate casing layer is then covered with a cover layer using either reaction injection molding or a casting process. In a casting process, the cover composition is dispensed into the cavity of an upper mold member. This first mold half has a hemispherical structure. Then, the cavity of a corresponding lower mold member is filled with the cover material, preferably the polyurea mixture. This second mold half also has a hemispherical structure. The cavities are typically heated beforehand. A ball cup holds the golf ball (core and overlying casing layer) under vacuum. After the polyurea mixture in the first mold half has reached a semi-gelled or gelled sate, the pressure is removed and the golf ball is lowered into the upper mold half containing the polyurea mixture. Then, the first mold half is inverted and mated with the second mold half containing polyurea mixture which also has reached a semi-gelled or gelled state. The polyurea mixtures, contained in the mold members that are mated together, form the golf ball cover. The mated first and second mold halves containing the polyurea mixture and golf ball center may be next heated so that the mixture cures and hardens. Then, the golf ball is removed from the mold. The ball may be heated and cooled as needed.

Test Methods

Hardness: The surface hardness of a golf ball layer (or other spherical surface) is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the core or on surface defects such as holes or protrusions. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface of the golf ball layer, care must be taken to ensure that the golf ball or golf ball subassembly is centered under the durometer indentor before a surface hardness reading is obtained. A calibrated digital durometer, capable of reading to 0.1 hardness units, is used for all hardness measurements and is set to take hardness readings at 1 second after the maximum reading is obtained. The digital durometer must be attached to and its foot made parallel to the base of an automatic stand. The weight on the durometer and attack rate conforms to ASTM D-2240. It should be understood that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball.” For purposes of the present invention, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. Surface hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value. The difference in “surface hardness” and “material hardness” values is due to several factors including, but not limited to, ball construction (that is, core type, number of cores and/or cover layers, and the like); ball (or sphere) diameter; and the material composition of adjacent layers. It also should be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other.

It is understood that the golf balls having a polyurea cover and/or intermediate layer described and illustrated herein represent only presently preferred embodiments of the invention. It is appreciated by those skilled in the art that various changes and additions can be made to such golf balls without departing from the spirit and scope of this invention. It is intended that all such embodiments be covered by the appended claims. 

1. A golf ball, comprising: a core; a polyurea intermediate casing layer produced by a reaction of ingredients comprising a first isocyanate, first amine-terminated polyisobutylene, and first amine-terminated cross-linking agent; and a polyurea cover material produced by a reaction of ingredients comprising a second isocyanate, second amine-terminated polyisobutylene, and second amine-terminated cross-linking agent.
 2. The golf ball of claim 1, wherein the core comprises polybutadiene.
 3. The golf ball of claim 1, wherein the first and second isocyanates are selected from the group consisting of MDI, H₁₂MDI, PPDI, TDI, IPDI, HDI, NDI, XDI, TMXDI, THDI, and TMDI, and homopolymers and copolymers and mixtures thereof.
 4. The golf ball of claim 1, wherein the first and second amine-terminated curing agents are selected from the group consisting of curing agent is an amine-terminated curing agent selected from the group consisting of 4,4′-diamino-diphenylmethane; 3,5-diethyl-(2,4- or 2,6-)toluenediamine; 3,5-dimethylthio-(2,4- or 2,6-)toluenediamine; 3,5-diethylthio-(2,4- or 2,6-)toluenediamine: 2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane; polytetramethyleneglycol-di(p-aminobenzoate); 4,4′-bis(sec-butylamino)-dicyclohexylmethane; and mixtures thereof.
 5. The golf ball of claim 1, wherein the core has a diameter of about 1.26 to about 1.60 inches.
 6. The golf ball of claim 1, wherein the intermediate casing layer has a thickness of about 0.015 to about 0.120 inches.
 7. The golf ball of claim 6, wherein the intermediate casing layer has a thickness of about 0.035 to about 0.060 inches.
 8. The golf ball of claim 1, wherein the cover has a thickness of about 0.015 to about 0.090 inches.
 9. The golf ball of claim 8, wherein the cover has a thickness of about 0.020 to about 0.040 inches.
 10. The golf ball of claim 1, wherein the core has a surface hardness in the range of about 30 to about 65 Shore D.
 11. The golf ball of claim 1, wherein the intermediate casing layer has a material hardness of about 45 to about 80 Shore D.
 12. The golf ball of claim 1, wherein the cover has a material hardness of about 40 to about 65 Shore D.
 13. A golf ball, comprising: a core; a polyurea intermediate casing layer produced by a reaction of ingredients comprising an isocyanate, amine-terminated polyisobutylene, and amine-terminated cross-linking agent; and a polymeric cover material, wherein the cover material comprises a thermoplastic or thermoset material and does not include a polyurea formed by reacting an isocyanate, amine-terminated polyisobutylene, and amine-terminated cross-linking agent.
 14. The golf ball of claim 13, wherein the core comprises polybutadiene.
 15. The golf ball of claim 13, wherein the cover material comprises a polyurethane resin.
 16. The golf ball of claim 13, wherein the cover material comprises an ionomer resin.
 17. The golf ball of claim 13, wherein the cover material comprises a blend of ionomer and non-ionomer resins.
 18. A golf ball, comprising: a core; a polymeric intermediate layer, wherein the intermediate layer comprises a thermoplastic or thermoset material and does not include a polyurea formed by reacting an isocyanate, amine-terminated polyisobutylene, and amine-terminated cross-linking agent; and a polyurea cover material produced by a reaction of ingredients comprising an isocyanate, amine-terminated polyisobutylene, and amine-terminated cross-linking agent.
 19. The golf ball of claim 18, wherein the core comprises polybutadiene.
 20. The golf ball of claim 18, wherein the intermediate layer comprises an ionomer resin.
 21. The golf ball of claim 18, wherein the intermediate layer comprises a blend of ionomer and non-ionomer resins. 